In the prior art, an elongated, extensible, boom has a fluid dispersing nozzle on the outer end thereof along with a piercing nozzle. Either nozzle can be used but they are used separately and almost never used together. Their use is directed to confront a single fire. Inasmuch as fires may erupt or break out at any moment in different adjacent or nearby spots or areas, it is impossible for the systems of the prior art to confront or fight two fires in different nearby areas simultaneously.
In U.S. Pat. No. 5,839,664, a piercing nozzle moves in a vertical plane only with respect to the longitudinal axis of the extensible boom. The fluid nozzle can be moved to a position 90° displaced from, or perpendicular to, the piercing nozzle to allow more space for the piercing nozzle to penetrate a necessary wall without damaging the fluid nozzle. Only one of the fluid nozzles can be used at any one time.
Further, extensible aerial booms are well known in the art as shown in U.S. Pat. No.'s 5,788,158 and 5,301,756. Each of these patents discloses a piercing nozzle at the end of an elongated boom. When used to pierce a wall such as the skin of an airplane, the longitudinal axis of the piercing nozzle must either be in longitudinal alignment with, or perpendicular to, the longitudinal axis of the boom. If these requirements were not so and the longitudinal axis of the piercing nozzle was out of alignment with the longitudinal axis of the boom, as the boom moves forward to cause the piercing nozzle to pierce the wall, a stress moment arm is placed upon the piercing nozzle and may snap if off of its mountings or otherwise damage it. This possibility of damage is shown in FIG. 14 of U.S. Pat. No. 5,301,756 and is discussed in column 10 therein. The same analysis applies to the longitudinal axis of the piercing nozzle not being perpendicular to the longitudinal axis of the boom. As the boom moves downwardly in an arc as shown in FIG. 12 in the '756 patent to force the piercing nozzle through the wall (or skin of an aircraft), the piercing nozzle can be damaged if its longitudinal axis is NOT perpendicular to the boom longitudinal axis. In order to minimize such possibility of damage, a slip-clutch is placed between the piercing nozzle and its boom attachment point.
Further, in the prior art, extensible booms move outwardly and inwardly at high speeds. To prevent damage to either the stable portion of the boom, the extensible portion, or the vehicle, sensors are placed on or associated with the extensible boom to detect its nearness to its limits. The sensor signals are then fed to a computer which tells the boom to immediately stop. Such sudden stops place a great deal of stress on the fluid discharge nozzles and other components by the sudden change of speed of the extensible boom.
In the U.S. Pat. No. 5,301,756 patent, the fluid nozzle and the piercing nozzle move together in both the vertical plane and horizontal plane but, again, only one nozzle can be utilized to dispense fluid at any one time. There is no possibility of individually controlling two nozzles to allow two adjacent or nearby fires to be attacked or fought simultaneously.
Finally, in U.S. Pat. No. 5,301,756, the outer boom is moved in the vertical plane by first and second link sections slidable within each other. The bottom end of the lower link is connected to the boom turntable while the outer end of the upper link is connected to the inner end of the upper boom. A hydraulic piston is coupled between the two slidable links to move the links with respect to each other to raise or lower the upper boom. This system completes its task well but corrosion internal of the slidable sections causes added stress to be placed on the links and requires difficult maintenance.
It would be advantageous to have an extensible upper aerial boom for pivotal mounting on the outer end of a lower boom that is attached at its inner end to a vehicle, the extensible upper aerial boom having at least two independently controlled fluid discharge nozzles to allow fires in two adjacent areas to be fought simultaneously; that had a hydraulically driven piercing nozzle to allow penetration of a wall without requiring the boom itself to provide the penetrating force; that had the extensible upper boom with a fixed portion and a moveable portion; and that had linear sensors associated with the hydraulic cylinders that move the lower and upper booms in a vertical plane